The current trend in microelectronic technology of decreasing device size and increasing integrated circuit complexity is placing ever increasing demands on the level of spatial uniformity required of the semiconductor starting material. Inhomogeneities in the semiconductor, present either after slice preparation or introduced during circuit manufacture can lead to unacceptable variations in device characteristics which may manifest themselves as either an initially unacceptable IC chip or perhaps even worse, the subsequent failure of an initially acceptable circuit. A need then exists for some means of semiconductor profiling to enable regions of suspect material to be identified early in the production cycle. Also the technique itself should introduce a minimum of damage into the sample under scrutiny.